SSL_get_errorSection: OpenSSL (3)
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NAMESSL_get_error - obtain result code for TLS/SSL I/O operation
int SSL_get_error(const SSL *ssl, int ret);
DESCRIPTIONSSL_get_error() returns a result code (suitable for the C ``switch'' statement) for a preceding call to SSL_connect(), SSL_accept(), SSL_do_handshake(), SSL_read(), SSL_peek(), or SSL_write() on ssl. The value returned by that TLS/SSL I/O function must be passed to SSL_get_error() in parameter ret.
In addition to ssl and ret, SSL_get_error() inspects the current thread's OpenSSL error queue. Thus, SSL_get_error() must be used in the same thread that performed the TLS/SSL I/O operation, and no other OpenSSL function calls should appear in between. The current thread's error queue must be empty before the TLS/SSL I/O operation is attempted, or SSL_get_error() will not work reliably.
RETURN VALUESThe following return values can currently occur:
- The TLS/SSL I/O operation completed. This result code is returned if and only if ret > 0.
- The TLS/SSL connection has been closed. If the protocol version is SSL 3.0 or TLS 1.0, this result code is returned only if a closure alert has occurred in the protocol, i.e. if the connection has been closed cleanly. Note that in this case SSL_ERROR_ZERO_RETURN does not necessarily indicate that the underlying transport has been closed.
- SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
The operation did not complete; the same TLS/SSL I/O function should be
called again later. If, by then, the underlying BIO has data
available for reading (if the result code is SSL_ERROR_WANT_READ)
or allows writing data (SSL_ERROR_WANT_WRITE), then some TLS/SSL
protocol progress will take place, i.e. at least part of an TLS/SSL
record will be read or written. Note that the retry may again lead to
a SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE condition.
There is no fixed upper limit for the number of iterations that
may be necessary until progress becomes visible at application
For socket BIOs (e.g. when SSL_set_fd() was used), select() or poll() on the underlying socket can be used to find out when the TLS/SSL I/O function should be retried.
Caveat: Any TLS/SSL I/O function can lead to either of SSL_ERROR_WANT_READ and SSL_ERROR_WANT_WRITE. In particular, SSL_read() or SSL_peek() may want to write data and SSL_write() may want to read data. This is mainly because TLS/SSL handshakes may occur at any time during the protocol (initiated by either the client or the server); SSL_read(), SSL_peek(), and SSL_write() will handle any pending handshakes.
- SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT
- The operation did not complete; the same TLS/SSL I/O function should be called again later. The underlying BIO was not connected yet to the peer and the call would block in connect()/accept(). The SSL function should be called again when the connection is established. These messages can only appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively. In order to find out, when the connection has been successfully established, on many platforms select() or poll() for writing on the socket file descriptor can be used.
- The operation did not complete because an application callback set by SSL_CTX_set_client_cert_cb() has asked to be called again. The TLS/SSL I/O function should be called again later. Details depend on the application.
- Some I/O error occurred. The OpenSSL error queue may contain more information on the error. If the error queue is empty (i.e. ERR_get_error() returns 0), ret can be used to find out more about the error: If ret == 0, an EOF was observed that violates the protocol. If ret == -1, the underlying BIO reported an I/O error (for socket I/O on Unix systems, consult errno for details).
- A failure in the SSL library occurred, usually a protocol error. The OpenSSL error queue contains more information on the error.
SEE ALSOssl(3), err(3)
HISTORYSSL_get_error() was added in SSLeay 0.8.